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<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/4.5.3/css/bootstrap.css" rel="stylesheet">
</head>

<body>
    <div class="container">
        <h2 class="page-header">Promise 封装 AJAX</h2>
        <button class="btn btn-primary" id="btn">点击发送AJAX</button>
    </div>
    <script>
        const btn = document.querySelector('#btn');
        btn.addEventListener('click', function () {
            // 创建Promise
            const p = new Promise((resolve, reject) => {
                // 1.创建对象
                const xhr = new XMLHttpRequest();
                // 2.初始化
                xhr.open('GET', 'https://api.apiopen.tp/getJoke');
                // 3.发送
                xhr.send();
                // 4.处理相应结果
                xhr.onreadystatechange = function () {
                    if (xhr.readyState === 4) {
                        // 判断状态码 2xx
                        if (xhr.status >= 200 && xhr.status < 300) {
                            // 控制台输出响应体
                            resolve(xhr.response);
                        } else {
                            // 控制台输出响应状态码
                            reject(xhr.status);
                        }
                    }
                }
            })
            // 调用then方法
            p.then(value => {
                console.log(value);
            }, reason => {
                console.warn(reason)
            })




        })
    </script>
</body>

</html>